That is a good suggestion, Teresa_Cyrus!
On this initial launch of the feature, users will be able to show/hide all declined meetings by tweaking the "Filter" tool in the ribbon. Unfortunately, it will apply to all declined meetings together, and not just a subset of them.
Since it seems you want to keep/preserve all your declined meetings, but selectively choose which ones to show/hide on the calendar surface, I do have some good news for you. It is not exactly what you are suggesting, but it will empower you to achieve similar results. We are finishing up some improvements to the Filter feature which will include persistence (your filtered settings do not get reset between sessions) and multiselect (you can combine multiple filter options). This means you will soon be able to apply different categories to the declined meetings you want and don't want to see, and then use the new filtering capabilities to show/hide just those subsets of declined meetings you care about.
As soon as the new filtering improvements are publicly available, I will come back here to announce them. I hope they help you! And if they don't, we will keep our minds open for feedback like yours on further potential improvements for declined meetings.
rgds,
Gio