[Question] Efficient shortcut for unstacking only parts of dimension?

Hi all, is there an efficient way to unstack only parts of a MultiIndex?

Consider for example the following array:

<xarray.Dataset>
Dimensions:                      (observations: 17525)
Coordinates:
  * observations                 (observations) MultiIndex
  - subtissue                    (observations) object 'Skin_Sun_Exposed_Lower_leg' ... 'Thyroid'
  - individual                   (observations) object 'GTEX-111FC' ... 'GTEX-ZZPU'
  - gene                         (observations) object 'ENSG00000140400' ... 'ENSG00000174233'
  - end                          (observations) object '5' '5' '5' ... '3' '3'
Data variables:
    fraser_min_pval              (observations) float64 dask.array<chunksize=(17525,), meta=np.ndarray>
    fraser_min_minus_log10_pval  (observations) float64 dask.array<chunksize=(17525,), meta=np.ndarray>

Here, I have a MultiIndex observations=["subtissue", "individual", "gene", "end"].
However, I would like to have end in its own dimension.
Currently, I have to do the following to solve this issue:

xrds.unstack("observations").stack(observations=["subtissue", "individual", "gene",])

However, this seems quite inefficient and introduces NaN's.

Output of xr.show_versions()

Start by reading xarray's stack and unstack entry points and how they handle pandas MultiIndex dimensions. Investigate whether a partial unstack can preserve the remaining observations without introducing NaNs; done means an efficient supported operation that places end in its own dimension while retaining the other levels.