Here's something almost trivial:

Writing on a tablet instead of a piece of paper

I think many mathematicians probably acquired a tablet (e.g. something with its own screen like an iPad, or the kind without a screen that plugs into your computer like a Wacom - forgive me for using brand names here) for the first time as a result of the pandemic, in order to simulate the 'chalkboard' teaching experience online.

Now, many of us have the opportunity to continue writing our not-fully-formed mathematical thoughts on a tablet, as opposed to say on a physical notebook that we were using before.

There are pluses and minuses. The pluses are that it's nice to have a systemic and organized record on your computer of various mathematical thoughts you've been exploring, and it's easier to edit notes on the computer. The one big minus I can think of is that I still find it slightly slower to write on a tablet than with a pen and paper.