Linux: Paths missing after toolbox installation

Let's say you want to use 'dtw' algorithm, but you don't have Signal Processing Toolbox.

>> dtw
'dtw' requires Signal Processing Toolbox.

Clicking on the link, opens Add-Ons manager, but the installation usually fails since the user running matlab usually doesn't have permissions to write to /usr/local/, where matlab is usually installed). Usin sudo won't help, since matlab is usually configured to be only used with a specific user.

To install a toolbox in Linux, you have to follow a woraround: https://www.mathworks.com/matlabcentral/answers/717063-linux-installing-new-toolboxes-on-an-existing-installation

After this, the plugin is instlaled only partiually. The files are placed to the correct location, but the paths are not configured. Upon Matlab restart, if I try to run a scrip from the new toolbox, I get a different error:

>> dtw
Unrecognized function or variable 'dtw'.

Is there any better workaround, than copying the paths from someone that already has the toolbox installed to my pathdef.m?

Also, is there any way to install toolbox to userspace, avoiding the need to grant user writing permission to /usr/local?