- Debugging.

- Move all \RequirePackages to commonincludes.def.

Manual.cls

@@ -1,5 +1,8 @@
 \NeedsTeXFormat{LaTeX2e}
-\ProvidesClass{PrimeTeX/Manual}[2025-08-16]
+\ProvidesExplClass{PrimeTeX/Manual}{2025-09-12}{1.0}{
+	A class creating for user manuals and other book-like documents to be
+	published by Prime Controls.
+}
 
 \RequirePackage{ifthen}
 
@@ -72,4 +75,16 @@
 	\ifthenelse{\boolean{isElectronic}}{#1}{#2}
 }
 
-\NewDocumentCommand{\rem}{+m}{}
+\NewDocumentCommand{\rem}{+m}{}
+
+\str_new:N \l_IncludeOnly_chapters_str
+
+% Wrapper for \includeonly.
+% If argument is empty, all chapters are included.
+% If the argument is not empty, only chapters that are listed are included.
+\NewDocumentCommand{\IncludeOnlyChapters}{m}{
+	\str_set:Nn \l_IncludeOnly_chapters_str {#1}
+	\str_if_empty:NF \l_IncludeOnly_chapters_str {
+		\expanded{\noexpand\includeonly{\l_IncludeOnly_chapters_str}}
+	}
+}