This happens when advance is made against a sales order or direct. The customer ledger won’t show the advance tax paid initially but after invoicing, the customer ledger is updated. Is this a bug or the default behaviour.
It looks like you’ve got some filters set on your General Ledger, but I can’t tell what they are from screenshot. If you remove the filters, are you able to see the two GST entries?
Correct, your GST account is not a party account, so it won’t show up in the General Ledger if you filter by party. Depending on your needs, you might be able to use something like the Sales Register, or you can create a custom report to organize the data however you’d like.