Increase key press delays for the contrl keys

I’m using Unity desktop. The foremost reason I use that because it enables me switching windows by pressing Super+N where N belongs to {0, 1, 2, 3 … 9}

The way I have optimized is by assuming, at most I will be using 10 apps in real life. So I made the dock hidden and keep switching to the apps I needed based on the preset location (1-PyCharm, 2-Terminator, 3-DBeaver, 4-Sublime, 5-Opera, 6-Zim, 7-Filemanager, 8-Slack, 9-Postman, 0-Telegram)

Now the problem is, when I switch windows quickly by pressing Super followed by a number, the trouble happens often, while pressing the combo (Super+N), I tend to release the Super key milliseconds prior to hitting the number.

Now the question is, how to add a timedelay for Super key so that it last 0.25 seconds longer even after it was released?