Hi timo. I have been using the "resume work" option in the right click menu for some time now, however I do see how the suggestion by Tobias to have a Change (switch) Task would be helpful. I see this being used when you have not had to use a particular task today and want to quickly switch from the current task to that new task.
Selecting 'Switch Task', probably from the right click menu also, would allow me to initiate a task quickly when for example, a customer calls and I want to record the time spent talking with them without being distracted by the extra steps of stopping the current task and selecting a new task for the call.
Please consider implementing the "Change/switch task" option that Tobias has suggested for inclusion in a coming update.