Easy way to limit CPU usage on apps

This is a pretty common problem: We have an app that’s doing a task that require really high processing power, like video encoding or compiling, which takes 100% of the CPU or GPU.
Sometimes, we might want to limit how much power it can draws, so the system is still usable while doing the task, or to prevent the system from overheat.

Annnnnd I can’t find a single GUI solution after 20 minutes of Googling.

Not saying it’s impossible, it just feels too convoluted for a problem this common, we can probably do better.
What I have in mind is like Filelight in Dolphin, it’s not necessarily a built-in solution, but it can be a simple package in System Monitor app, that’d allow me to right click on the process and set the maximum % it can uses.

…I have no idea how practical it is. But hey, the tag said brainstorm.

The old system monitor could do this. Can’t recall why it isn’t in the new one.

https://bugs.kde.org/show_bug.cgi?id=457237

There are alternative monitors or tools than can do this.

alternative monitors or tools

Can you provide examples?

A few examples are linked in the thread from my previous post.

qps from LxQT
htop
btop
and probably dozens of others.

qps - Is this a LxQT exclusive app? How do I get it to run in Plasma?
htop, btop - I see it’s monitoring and can kill process, but I don’t see a way to limit % usage of specific process.

You renice the process, which changes the priority. Which is what the old tool used to be able to do, and Qps can.

Do I have to build qps myself?

Can’t say.
It is available in the standard Ubuntu archive, going back a ways, so I’d imagine it might be in most distros.