You can move queue tables online using DBMS_redefinition. MOS note 1410195.1 has a detailed description of the process and the code for a move_qt_pkg package for different versions to simplify this.
https://support.oracle.com/knowledge/Oracle%20Cloud/1410195_1.html If all you want to do is reset the HWM and reclaim space in the table, you can do this as described in doc 421474.1:
In 10.2 onwards in when the queue table objects are stored in ASSM tablespaces you can do the following for the single and multi-consumer queue tablesalter table <queue_table_name> enable row movement;
alter table <queue_table_name> shrink space cascade;
alter table <queue_table_name> disable row movement;
https://support.oracle.com/knowledge/Oracle%20Database%20Products/421474_1.html When you get to newer versions, there is a procedure in DBMS_AQADM to do this:
Newly database versions from 19c and onward can take advantage of the newly added procedure DBMS_AQADM.MOVE_QUEUE_TABLE to achieve such requirement in an easy and straightforward way. Note that two additional database patches are required for it to work within 19c and 21c databases: Patch 36051247 & Patch 34774667. Patches are not required for 23ai database https://support.oracle.com/knowledge/Oracle%20Database%20Products/304522_1.html