Show period in progress in retention table

[paolodamico]

Is your feature request related to a problem?

We currently show that a period is in progress in line charts (including the partial retention cohorts graph) by showing the in progress segment with a dotted line. We should do the same in the retention table.

Describe the solution you'd like

We should clearly show which period is in progress in the retention table. This particularly helps users understand which numbers are still subject to change.

Thank you for your feature request – we love each and every one!

[EDsCODE]

#2995