Here you can download a gskz file, which is a GSAK installation file, that will install all the necessary macro files to the correct GSAK folders.
I'm not going into details, on how to filter geocaches in GSAK, but when you wish to use the macro, select Macro→Run/Manage (Ctrl+M), and we'll find the macro in the list and run it.
The macro looks like this, and before we can do annything whe need an Accesstoken from cachetur, so we click Administer Accesstoken, and fill in our cachetur username and password, and click Get access token (on my setup we can see on top that the accesstoken allready exists)
After we have gotten our Accesstoken, we return to the startmenu. This menu let us choose to create a filter based on a trip route, fetch caches from a trip on cachetur, or sed caches to an existing trip on cachetur
Here you may send either the current cache in GSAK, or the entire current filer, by selecting your trip/list in the dropdown menu. The caches will appear at the bottom of your trip/list, or where you have selected the Insertion point for new waypoints