- To which new interface of the legacy Windows desktop App Spiceworks Help Desk 7.5 do you refer?
I haven't seen and updates nor interface changes for this legacy edition of Spiceworks. And Spiceworks has promised to no longer deliver any updates after it aborted its active development back in 2018, nor after expiry of support by end of last year. I only see features vanishing away as available integrations with 3rd party solutions become incompatible with such 3rd party solutions due to Spiceworks refusal to update any longer. And with several tight integrations, updates would be difficult to achieve without side-effects on other implemented features.
This legacy Windows Spiceworks Help Desk edition is the only one with support for sub-tickets. That's why it was obvious that you were referring to this edition despite not explicitly disclosing the Spiceworks edition.
I only know of an interface change to new interface in the public Cloud edition Spiceworks Cloud Help Desk (CHD) and its mobile apps. But these have never claimed to support sub-tickets. Those Spiceheads wanting sub-tickets implemented for CHD have voted up the corresponding feature request, in the hope to getting it implemented before that edition reaches end of support. Those needing such feature without such hope or patience have migrated to 3rd party solution.
Those waiting for implementation of such feature with hope don't know the answer to your question for the case of CHD neither as the corresponding release notes with documentation of such new feature has not yet been released.
I don't know why you are asking specifically for sub-tickets nor for which use case. You may check if tasks in CHD may provide some limited workaround for existing limitation and may work for your undisclosed use case too. But I haven't seen documentation of CHD tasks neither.