Status: Not Portable. Writes to C:\Users\USERNAME\AppData\Local\Reliak\ReliakTimer.exe_Url_5mf2cjycbum55drb1nyqnc2mm23onne5\1.0.0.0\user.config
Appears to require dotNET v4.5 and does not minimize to the system tray. which would be helpful to keep it from interfering with the work it's helping you manage. Unfortunately, does not appear to be in development anymore.
Site: https://sourceforge.net/projects/reliak-timer/
Background: I've been frustrated by Electron-based programs taking over a huge number of notepad functions, which I usually think of as one of the lowest resource usage tools on your computer. The functions of a basic notepad haven't changed since the mid-90s so this should be at the level of a calculator. Yet here we have huge downloads, RAM usage, and more.
Just below notepads, I assumed alarm clocks would be the lowest until I found a crop of simple timer programs with 50+ meg downloads.
Two of the worst offenders both push into a 150 meg download: Astrofocus and Pomy:
https://www.softpedia.com/get/Desktop-E ... Pomy.shtml
https://www.softpedia.com/get/Desktop-E ... used.shtml
It's here that I found ReliakTimer, which is 1% of those, just about fitting on an old 1.44 meg floppy disk.