Re: "Garageband doesn't retain the Save to Files location"
       Sometimes things are smoother if we work the way the software has been set up to work.
       Apple Support's online articles (links below) often provide step-by-step working methods, or share tips.
Wondering if, in Garageband, you create a project for each podcast:
See: Create and save projects in GarageBand on Mac - Apple Support
Eg says:
"Save the current project:
- In GarageBand on Mac, choose File > Save.
 
The first time you save a new project, the Save dialogue appears. 
In the Save dialogue, you can type a name for the project and choose the location to save it."
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Re:  "... every time I need to Export to Disk I have to delve into the disk and folder location for every save".
You may want to export the complete podcast project, or export a part:
See how to: Export songs to disk or iCloud from GarageBand on Mac - Apple Support
Eg: says:
"The entire project, from the beginning to the end of the last region, is exported as an audio file. 
Any silence at the beginning or end of the project is trimmed."
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Resource: : We can use the "Table of Contents" or the search field  to zero in on particular methods:
                     in the GarageBand User Guide for Mac
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Garageband Support website: (info. / support / contact options tc.) GarageBand – Official Apple Support