XnView Software

oops, there is a button "APPLY". It has to be pressed!
Sorry folks!

The other functions save ok, eg cropping, rotation, colour adjustment.
It was saved to the folder from which it came.

The Linux program GIMP and its simpler cousin Glimpse do a fairly good job, but it is a real pain to use and lacking in functuality.
There are others but that claim to do Text but not very effectively.
So we are left with why does XnView not save text edits - or am I doing something wrong?

In Windows you can enter text in "Paint". I'm looking for a Linux program that can do it.

Yes those little boxes, you have to find out what they do by trial and error. The tick boxes determine if you have a solid or transparent background to the text.
Were you able to save it?

In fact I am using Version 1.3.1 64bits (Oct 12 2022)

Edit>Add Text.
The word "HIDDEN" appears in the new version, but does not survive saving.

XnView MP Linux
Version 1.0 64bits (Apr 29 2022)

I added text as shown in the attachment, and saved the file.
When I open the file in any program including XnView, the text is not shown.
It doesn't matter what format I save in.