1 Option:
If you want to custom print format then add a column and added a condition like if Item tax Template 18% then 18% is shown in GST% columns.
And you can also calculate the GST amount in different columns.
2 Option:
Create a custom field like GST% in the sales invoice items and also set the custom field in Item Tax Template and fetch from condition set in GST% in the sales invoice items.
When you select the Item Tax Template then automatically % is shown in the custom field and another custom field adds like the GST amount. And set your condition according to GST Amount.
Then go to your print format and added item columns like GST% and GST amount. Reload your system and check your GST Invoice print format.