diff --git a/src/libslic3r/Preset.cpp b/src/libslic3r/Preset.cpp
index de5dcb991e..cf065536cf 100644
--- a/src/libslic3r/Preset.cpp
+++ b/src/libslic3r/Preset.cpp
@@ -508,10 +508,11 @@ void Preset::normalize(DynamicPrintConfig &config)
     handle_legacy_sla(config);
 }
 
-std::string Preset::remove_invalid_keys(DynamicPrintConfig &config, const DynamicPrintConfig &default_config)
+std::string Preset::remove_invalid_keys(DynamicPrintConfig &config, const DynamicPrintConfig &default_config,
+                                        const DynamicPrintConfig *added)
 {
     std::string incorrect_keys;
-    for (const std::string &key : config.keys())
+    for (const std::string &key : (added != nullptr ? *added : config).keys())
         if (! default_config.has(key)) {
             if (incorrect_keys.empty())
                 incorrect_keys = key;
@@ -2871,6 +2872,19 @@ std::pair<Preset*, bool> PresetCollection::load_external_preset(
     return std::make_pair(&preset, false);
 }
 
+Preset& PresetCollection::append_preset(const std::string &path, const std::string &name, DynamicPrintConfig &&config)
+{
+    lock();
+    m_presets.emplace_back(Preset(m_type, name, false));
+    Preset &preset = m_presets.back();
+    preset.file = path;
+    preset.config = std::move(config);
+    preset.loaded = true;
+    preset.is_dirty = false;
+    unlock();
+    return preset;
+}
+
 Preset& PresetCollection::load_preset(const std::string &path, const std::string &name, DynamicPrintConfig &&config, bool select, Semver file_version)
 {
     lock();
diff --git a/src/libslic3r/Preset.hpp b/src/libslic3r/Preset.hpp
index b554d6067f..b040ec04e6 100644
--- a/src/libslic3r/Preset.hpp
+++ b/src/libslic3r/Preset.hpp
@@ -445,7 +445,10 @@ public:
     static std::string                      remove_suffix_modified(const std::string& name);
     static void                             normalize(DynamicPrintConfig &config);
     // Report configuration fields, which are misplaced into a wrong group, remove them from the config.
-    static std::string                      remove_invalid_keys(DynamicPrintConfig &config, const DynamicPrintConfig &default_config);
+    // `added`, when given, is the diff applied over a copy of default_config, and only
+    // its keys are checked, since no other key can be missing from default_config.
+    static std::string                      remove_invalid_keys(DynamicPrintConfig &config, const DynamicPrintConfig &default_config,
+                                                                const DynamicPrintConfig *added = nullptr);
 
     // BBS: move constructor to public
     Preset(Type type, const std::string &name, bool is_default = false) : type(type), is_default(is_default), name(name) {}
@@ -940,6 +943,12 @@ private:
         return a.name < b.name;
     }
 
+    // Add a preset at the end rather than at its place in the order, which turns one
+    // O(n) insertion per preset into a single sort for a caller installing a whole
+    // vendor. The collection is unsorted, and find_preset() unusable, until
+    // sort_presets() runs.
+    Preset& append_preset(const std::string &path, const std::string &name, DynamicPrintConfig &&config);
+
     // Sort presets: filament presets use generic-first ordering, others sort alphabetically.
     void sort_presets() {
         if (m_type == Preset::TYPE_FILAMENT)
diff --git a/src/libslic3r/PresetBundle.cpp b/src/libslic3r/PresetBundle.cpp
index a972bc72e9..b7b2053ba5 100644
--- a/src/libslic3r/PresetBundle.cpp
+++ b/src/libslic3r/PresetBundle.cpp
@@ -6692,24 +6692,21 @@ PresetBundle::PresetInstall PresetBundle::resolve_vendor_preset(
         out.included->apply_only(out.config, out.config.diff(presets_collection.default_preset_for(out.config).config));
     }
     extend_default_config_length(out.config, true, *default_config);
+    // Report configuration fields, which are misplaced into a wrong group, before
+    // Preset::normalize derives keys from them. An include diff holds only keys of the
+    // collection default, so only the entry's own keys can be missing from default_config.
+    std::string incorrect_keys = Preset::remove_invalid_keys(out.config, *default_config, &entry.config_src);
+    if (!incorrect_keys.empty())
+        out.errors.push_back(std::string(__FUNCTION__) + ": The config " + subfile + " contains incorrect keys: " +
+                             incorrect_keys + ", which were removed");
     if (entry.instantiation == "false" && "Template" != vendor_name) {
-        // Report configuration fields, which are misplaced into a wrong group.
-        std::string incorrect_keys = Preset::remove_invalid_keys(out.config, *default_config);
-        if (!incorrect_keys.empty())
-            out.errors.push_back(std::string(__FUNCTION__) + ": The config " + subfile + " contains incorrect keys: " +
-                                 incorrect_keys + ", which were removed");
         out.config_only = true;
         return out;
     }
     if (out.config.has("alias"))
         out.alias = (dynamic_cast<const ConfigOptionString *>(out.config.option("alias")))->value;
-    Preset::normalize(out.config);
 
-    // Report configuration fields, which are misplaced into a wrong group.
-    std::string incorrect_keys = Preset::remove_invalid_keys(out.config, *default_config);
-    if (!incorrect_keys.empty())
-        out.errors.push_back(std::string(__FUNCTION__) + ": The config " + subfile + " contains incorrect keys: " +
-                             incorrect_keys + ", which were removed");
+    Preset::normalize(out.config);
 
     if (presets_collection.type() == Preset::TYPE_PRINTER) {
         // Filter out printer presets, which are not mentioned in the vendor profile.