Please Adobe...

Unless I am misunderstanding what you are after, this always used to be available as one of the options for "Mix Paste". Has it been removed in later versions then?

The options were:

Insert:- Inserts audio at the current location or selection, replacing any selected data. If no data is selected, Adobe Audition inserts audio at the cursor location, moving any existing data to the end of the inserted material. <--- THIS ONE

Overlap:- Mixes audio at the selected volume level with the current waveform. If the audio is longer than the current waveform, the current waveform is lengthened to accommodate the pasted audio.

Replace:- Overdubs the audio beginning at the cursor location, and replaces the existing material thereafter for the
duration of audio. For example, pasting 5 seconds of material replaces the first 5 seconds after the cursor.

Modulate:- Modulates the audio with the current waveform for an interesting effect. The result is similar to overlapping, except that the values of the two waveforms are multiplied by each other, sample by sample, instead of added.

Yes, PLEASE!

Great to have the ´Ripple delete´-option. But very strange not to include the logical counterpart ´Ripple insert´. Somewhat like an arm with a biceps but no triceps.

Yes, this. It is frustrating when editing a podcast in multitrack to have no quick option to insert, for example, a short clip of room noise when you need the pause between two speakers to be longer. This shouldn't require the workaround it does.