You can carry over 100% of your previous years losses. 2020 Schedule D instructions has the Capital Loss Carryover Worksheet. Complete that, which will allow you to enter your short-term and long-term capital loss carryover amounts on Lines 6 and 14 of your 2020 Schedule D. Unfortunately, I believe not using the $3,000 maximum loss last year does not mean you get to add it to the $3,000 maximum loss this year - Line 21 on your schedule D will explain you still only get to use a $3,000 maximum loss this year. I am not aware of an allowance for claiming a previous year's maximum loss in the current year.
BTW, if you use the Schedule D Capital Loss Carryover Worksheet and enter the total losses on your Schedule D each year, it gives you a really easy starting point to keep your loss total rolling forward. If you have $10,000 of losses, then sell equities to realize some gains to "use up" that loss - and you will have no net gain to have to pay taxes on.
