This non-usable leftover is also called “dust”.
Binance has a brilliant feature: it allows you to convert the dust into BNB. We recommend using this feature and then converting BNB into the coin you actually need.
The same as Binance OKEx has the option to convert the dust to its coin (OKB). You can find more details here: https://www.okex.com/academy/en/how-to-convert-small-balances-into-okb-on-okex.
Please note that you’ll need to verify your OKEx account to convert the coins. It can be done on Funding account only.