allow a blank value for the value for "Enter text from" so it will change any text selected to the entered text
I don't know anything about the subtext macro, but my TextReplace macro may be a suitable replacement in some circumstances:
TextReplace was released a few months ago and was basically written as an exercise to re-familiarize myself with DCAL for Delphi after spending many months working on the Space Planner macro using Classic DCAL.
One of the limitations of DCAL for Delphi is that is does not include the standard selection functionality (i.e. the is no equivalent for the Classic DCAL GetMode procedure that implements the entity/group/area/fence selection), and as a result of this a major limitation of the TextReplace macro is that it cannot select entities to process based on these criteria. It can process all entities on a single or multiple selected layers.
I have added the ability to specify a blank 'Search For' string in v1.1 of this macro, and in this case it will replace all text on the selected layer(s) with the 'Replace With' string, but will prompt to confirm every replacement. Not a particularly elegant solution if you only want to process a handful of text entities on a layer that includes a large amount of text, but it may the useful to you...
You can find the TextReplaceMacro at http://www.dhsoftware.com.au/treplace.htm
I may look at allowing replacement on entities selected one by one in the future....