If you've got a little money to throw at this, passing the time gets a lot easier. Here are our favorites:
Learn a Language
Muzzy by the bbc is an amazingly comprehensive language learning program that can be used by very young children. They offer lessons in Italian, French, Spanish, German, Mandarin and Korean and you can view the videos on tablet, computer or Roku/FireTV. We've found the videos engaging enough to keep our daughter occupied and easy to understand on her own.
Toys for Self-Directed Play
If you have the cash and space to keep some new toys, there's a bunch of things on this list that I hadn't seen before and some my daughter loves. Of course, as with any toy, your kids "self-directed" mileage may vary so I encourage you to read reviews and watch videos so that you can get a better sense of whether or not a particular toy will appeal to your child: https://modernparentsmessykids.com/mpmk-2013-gift-guide-top-learning-toys-for-quiet-time-independent-play/
Let your Kids Clean
This sounds like a joke but I promise you that if you don't focus on whether or not they are "doing it right" and get them kid size equipment, most kids love cleaning. This is particularly helpful if you also decide to let them play with pantry items (see next entry). Here are some kid size cleaning tools we like (not an affiliate link - if you can find it somewhere else cheaper, let me know): Little Helper Broom Set
Raid the Pantry
If you don't have anxiety about running out of baking basics and don't care about the mess (or you can get your kids to clean it up), I recommend letting your kids play with flour, cornstarch or anything else that won't get them sticky or be too tempting to eat. Note: I have recipes for things like slime/ooblek, cloud dough and playdough in the "Time and Money" page
Water Table/Sand Table
If its nice enough to go outside where you live, investing in one of these may not be a bad idea - a single toddler can usually spend at least 30 minutes. If you have more than one kid, it can usually be pushed to an hour. Simplay3 Kids Indoor Outdoor Sand and Water Activity Table with Storage I really like that one because its so basic that you can use it for other things later and just throw in items you already have like kitchen utensils, bath toys etc. Looking for sand?
What, no TV or Movies?
I'm not judgey, if you think that renting some movies or subscribing to Disney+ will buy you some time, by all means, do it. Personally, I've been burned too many times to recommend this. I've rented so many movies thinking that it would keep my daughter quiet during a conference call or distracted while I worked. IT NEVER HAS.
I wish I had time to write up everything but, I don't (at least not yet, let's see how long this lasts). So here's a lot of other suggests with links when needed: