In Win 10 Mobile was setting for developers where I could set the count of crash dumps must be saved on a device. After installing Creators Update that setting disappeared
Microsoft changed this since Windows 10 Mobile Creators update v1703. After activating Device Portal use your development PC and open the Device portal Url that is shown on the phone.
Now the updated device portal has an entry Crash data
which you have to click
Now it takes around 30 seconds where the phone enumerates all sideloaded apps, lists them and offers you a checkbox to create dumps for each sideloaded app
So with the updated device portal you can now control the dump creation per sideloaded app instead of a global dump count. But I have no idea how many dumps are created, because I haven't got a crash.