I just realized that:
if a plugin has dependencies, and therefore there should be the possibility of having a relative path to facilitate its portability, it is the plugin that should provide that possibility, and not the DAW.
For example, Yoshimi allows you to set a relative path "./" and it will search for the banks and presets within the project.
It is not a problem of the DAW (Qtractor in this case). Since there will be plugins that prefer, to facilitate portability, to save their samples in presets, or in the same folder as the plugin to avoid the conflict of duplicate resources.
In other words, this solution is: encapsulate the samples in reference to the plugin, not to the project. If you want to make your project portable, save, distribute your samples within presets along with the project, not within the project.
Conclusion: Unfortunately I do not find any plugin that completely satisfies this portability. It is something that seems not to be taken into account when developing plugins.
I just realized that:
if a plugin has dependencies, and therefore there should be the possibility of having a relative path to facilitate its portability, it is the plugin that should provide that possibility, and not the DAW.
For example, Yoshimi allows you to set a relative path "./" and it will search for the banks and presets within the project.
It is not a problem of the DAW (Qtractor in this case). Since there will be plugins that prefer, to facilitate portability, to save their samples in presets, or in the same folder as the plugin to avoid the conflict of duplicate resources.
In other words, this solution is: encapsulate the samples in reference to the plugin, not to the project. If you want to make your project portable, save, distribute your samples within presets along with the project, not within the project.
Conclusion: Unfortunately I do not find any plugin that completely satisfies this portability. It is something that seems not to be taken into account when developing plugins.