When planning, I typically use 3 levels:
Topic (one competence aim) - sub-topic/plan - lesson.
A topic usually consists of several plans.
These plans usually take a few lessons to complete.
Individual lessons are not singled out.

If I want to connect the planner to the calendar, one plan has to cover one lesson only. This means that if I want to spend e.g. 3 lessons on one text, which today typically corresponds to one plan, I have to divide this plan into 3 smaller plans. These may in part contain some of the same resources or activitie, which creates unnecessary disorder in the planner. All resources and tasks linked to this particular text belong together as one unit.

Suggestion 1:
It should definitely be possible to connect a plan lasting more than one day to one or several calendar events.
- I could then choose to connect the plan only to the lesson corresponding with the end date of the plan (if the calendar focuses on homework).
- I could also add the same plan to all the lessons that we spend on that sub-topic/plan.

Also, some lessons are divided into at least 2 separate sections. I may want to spend one part of the lesson on a grammatical topic and the rest on culture.
The way I use the planner today, I let 2 plans stay active that particular lesson - one from the topic "grammar", and another from the topic "culture".
The planner on the course dashboard then looks well organized. We start on top of the list and work our way down.

By structuring it this way, it is also easy for the students to find all of this year's grammar if they need to get some repetition. They find all plans (sub-topics) if they open the planner and find the topic "grammar".
With the automatically generated tree structure, they can also find everyting in one folder.
This overview is easily accessable, even though grammar has been taught in-between other topics throughout the whole year.

Suggestion 2:
It should also be possible to add more than one plan to the same calendar event.