how to make xyplorer treat extension as another extension

[xnmp]

i want to duplicate an extension to another
such as making xy treat png1 as the same as png
this mean preview,floating preview, open with xyplorer still work with png1 like png
but not have affect to another program/application (other application still treat png1 as png1,not png)
is it possible ? thanks

[SkyFrontier]

I'm trying to work this thing around but realized there are some... behaviors I wasn't expecting.

1. a known .png once renamed to .png1 (later to .pnx, assuming there were a 3-digit internal limit) will not be previewed anymore via PFA by #178, File / Floating Preview, nor by #177, File / Quick File View, neither by #1003, Miscellaneous / Preview / Full Screen Preview. Perhaps an external viewer may or may not do the job, but since on the field there are no certainties on what will be available on each machine, I'd prefer to rely on XYplorer own engine as much as I can. So... what could be done here?

2. I realized "previewed formats" (under Configuration) has a role here. Before setting association types, Quick File View pops showing a raw view of the file (even with "text files" category unticked), which is useless. After the association is made, Full Screen Preview or Floating Preview pop as expected but with a "No Preview Available" warning, blank (dark, in fact). What's the way around, then?

2.1 Can custom/undefined extensions be added to "previewed formats" listing on the fly, say by sc setting?

Thanks in advance.