Created attachment 107027 [details] Visual proof of error given. Kdenlive 17.04.3 cannot change the project cache folder to one located on an external hard drive.
Please try with the actual Kdenlive version 18.08.2
It seems that this report is related to very old unmaintained version. A lot changed since then, especially the timeline got a complete rewrite and it is likely that this has been fixed. Feel free to reopen this bug or create a new report if this is still happening with the latest version (https://kdenlive.org/en/download/)