Documentation improvements

doc/org.texi

@@ -4079,15 +4079,18 @@ starting with the letter @samp{W}.
 @cindex category, require for tags/property match
 @vindex org-odd-levels-only
 You can also require a headline to be of a certain level or category, by
-writing instead of any TAG an expression like @samp{LEVEL=3} or
+tapping into the syntax of property searches (@pxref{Property searches})
+and writing instead of any TAG an expression like @samp{LEVEL=3} or
 @samp{CATEGORY="work"}, respectively.  For example, a search
 @samp{+LEVEL=3+boss/-DONE} lists all level three headlines that have the
 tag @samp{boss} and are @emph{not} marked with the TODO keyword DONE.
-In buffers with @code{org-odd-levels-only} set, @samp{LEVEL} does not count
-the number of stars, but @samp{LEVEL=2} will correspond to 3 stars etc.
+In buffers with @code{org-odd-levels-only} set, @samp{LEVEL} does not
+count the number of stars, but @samp{LEVEL=2} will correspond to 3 stars
+etc.
 
 Accessing TODO, LEVEL, and CATEGORY during a search is fast.  Accessing any
-other properties will slow down the search.
+other properties will slow down the search for the first property
+accessed.  Any additional property tests are cheap.
 
 @node Properties and Columns, Dates and Times, Tags, Top
 @chapter Properties and Columns
@@ -6237,9 +6240,10 @@ and TODO indicate next actions.  The tag @@SHOP indicates shopping and
 is a next action even without the NEXT tag.  Finally, if the project
 contains the special word IGNORE anywhere, it should not be listed
 either.  In this case you would start by identifying eligible projects
-with a tags/todo match @samp{+PROJECT/-MAYBE-DONE}, and then check for
-TODO, NEXT, @@SHOP, and IGNORE in the subtree to identify projects that
-are not stuck.  The correct customization for this is
+with a tags/todo match@footnote{@ref{Tag searches}}
+@samp{+PROJECT/-MAYBE-DONE}, and then check for TODO, NEXT, @@SHOP, and
+IGNORE in the subtree to identify projects that are not stuck.  The
+correct customization for this is
 
 @lisp
 (setq org-stuck-projects

lisp/org-agenda.el

@@ -380,7 +380,8 @@ you can then use it to define a custom command."
   '("+LEVEL=2/-DONE" ("TODO" "NEXT" "NEXTACTION") nil "")
   "How to identify stuck projects.
 This is a list of four items:
-1. A tags/todo matcher string that is used to identify a project.
+1. A tags/todo/property matcher string that is used to identify a project.
+   See the manual for a description of tag and property searches.
    The entire tree below a headline matched by this is considered one project.
 2. A list of TODO keywords identifying non-stuck projects.
    If the project subtree contains any headline with one of these todo