After printing my Invoice Posting Journal & Manual Cheque Posting Journal it no longer offers the option to clear.
How do I clear these journals?

Look in the Company Profile on the "System/Report Options" tab. You will find a new option "Allow Post Journal purge".

But why purge Posting Journals? Why not print the hard-copy, then let the journals accumulate? At year-end, print all Posting Journals to PDF files. That gives you a permanent, searchable record of all postings during the year.

This is also a new product for Adagio that will automate the printing to PDF files on an ongoing basis during the year.