You should define proper Layer Extensions in the Layer Settings Dialog for all your Layers. Then use the Filter button in the upper right corner button of the Dialog.
The way you have to use it is you have to select a Layer that has the extension you still want to see (e.g. "CONCEPT"), then select the Filter by Extension option in the upper right button. Since at the activation of the option the selected Layer had the extension "CONCEPT", all Layers with the extension "CONCEPT" will stay displayed while all other Layers will become hidden.
This way I think you can achieve what you want.
There is another thing you can do to make this work even better. See, all those currently non-relevant layers will still appear in Layer pop-ups, even though they are not relevant for your Phase. So what you can do is you can create a Layer Combination in which all those other non-relevant Layers are locked.
Then, in the Work Environment Dialog, you can go to the "Dialog Boxes and Palettes" page and check the "Hide Locked Layers in Pop-up Palettes" checkbox. This way those locked Layers (which are not relevant for your current Phase) will not appear even in Layer Pop-ups.
(Of course it is easy to make them appear at any time since you just need to switch to a Layer Combination in which they are not locked and they will appear in those Layer Pop-ups.)
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