If you combine @ccstone’s macro with the appropriate trigger, then it works like in Word – more or less.
This one for example triggers when I release the left button of my USB mouse. You may have to adapt it to your device.
I said “more or less” because for me it only works properly when I select by dragging, not by double clicking.
Put it into a group where you set the applications where it should be available, and set up the group so that you can easily enable/disable it:
Here is the example for Nisus: [test] Highlighter.kmmacros (3.8 KB)
Edit:
If your word processor has its own highlighting function, then it is better to use that (instead of styling the text via KM). For example for Nisus Writer: