Mark the selected FoldingText line as a heading (or deepen its heading level) – simple script for keyboard assignment

make_or_deepen_header.applescript

-- Change first selected node to heading, 
-- or deepen level if already heading

-- DEV 1.1 Script

property pstrType : "heading"

on run
	tell application "FoldingText"
		-- CHECK THAT THERE IS A DOCUMENT
		set lstDocs to documents
		if length of lstDocs < 1 then return
		
		-- READ THE ID TYPE AND LEVEL OF THE SELECTION
		tell item 1 of lstDocs
			set {strID, strType, lngLevel} to {|id|, |type|, level} of item 1 of ¬
				(read nodes at path nodePath of (read selection))
			
			-- DECIDE WHETHER TO CHANGE TYPE OR DEEPEN THE EXISTING LEVEL
			if strType ≠ pstrType then
				set recChanges to {|type|:pstrType}
			else
				set recChanges to {level:lngLevel + 1}
			end if
			
			-- AND MAKE THE CHANGE
			update nodes at ids {strID} with changes recChanges
		end tell
	end tell
end run

Simple script for keyboard assignment

Function

Quickly flags the selected line as a header (rather than moving to start of line, removing any existing list or comment formatting and typing #).
If the selected line is already a header, it deepens the heading level (adds a further #).