XnView Software

Sticky Note Mode: hide all border, always on top
This will be very useful when place some useful tool image on screen

Demo of sticky note mode for xnview scenario:



Example of sticky note mode of Notepad++ and potplayer

In case anyone needed this, I found a perfect alternative to this: Snipaste
https://www.snipaste.com/

+1
for Frameless (borderless) mode (F10) like in Nomacs, ImageGlass
'Always on top' command already available (Settings > Toolbar or Context menu)