Thanks for all this music[al] info!
I do use iTunes to convert aif 44 files to aif 48 and so make the audio fit for FCPX. I do have with me a free AUDIO CONVERTER LITE app that is downloadable from the App Store. It has an impressive performance with an ability to receive a variety of audio inputs and export them out also in various formats. Whether this converter will work in Ventura, I don't know yet. However, you're pointing out Audacity's ability to deliver in this matter has been to me instructional.
Regarding iPhone backup feature of iTunes, I have learnt that you have to go to the finder window, select general, select your device [this procedure is for Macs having OS versions 10.15 and above] and choose back up that can even be password encrypted. So, loss of iTunes will not trouble me in this matter when upgrading to Ventura.
But Rode recordings from my SmartLav into my Rode App presents a different cup of tea. The recordings made do not appear easily for us to select and share the file, but the Rode folks have devised several other options to allow users to get their recordings into their computers, one of the options being iTunes that recognises the device when connected by usb and allows syncing. They have another option by which a recording can be shared online and downloaded, a tedious roundabout manner that is difficult to get done when there in no internet. I have written to Rode support yesterday regarding this matter and hope to get their reply to this problem of file transfer to my computer sans iTunes.
Your pointer towards the new features in FCPX pertaining to the scene removal mask has set my mouth watering. I have been aware of the many new features introduced in FCPX and GarageBand that I was missing out on, but, jumping from a 32-bit to 64-bit architecture involved a lot of calculations. As of now, as stated in the OP, I am very well satisfied with my creative works in GB and FCPX and the computer has been very stable. But of late I have been realising that I was missing out on many new developments. When trying to download audio plugins [usually I download only the free ones:)] I am presented with this info: works only in OS 10.15 or later. Perhaps now is the time for me to make the hop. Reading the 'troubles' users are facing with the newer versions, I was hesitant to make a decision to migrate. However, you replies in this thread have greatly encouraged me, quelled my fears. Thanks for taking so much of pains to answer and reassure.
Regards and take care
Dr. Somanna