On your Mac you can easily tag your transactions with #tags.
There are two options to tag your transactions. First choose the account in the list of your accounts.
1. Tag one transaction
If you move the mouse over a transaction in the list of transactions in your account, the button 'Add Tags' will appear.
Click on that button an start entering your tag (#). You can add an idividual tag, by entering #yourtag, then press the 'Enter-key' and then 'Done'.
2. Tag more transactions at once:
Press and hold the cmd-key and then mark the transaction you want to tag.
At the ende of your transaction list you will find the Tag-Symbol. Here you can add tags the same way as you do with a single transaction. You can add an idividual tag, by entering #yourtag, then press the 'Enter-key' and then 'Done'.