[the_other_guy]

it is as easy as any widget that kodi uses

xml:


<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>

<smartplaylist type="movies">

    <name></name>

    <match>one</match>

    <rule field="genre" operator="is">Documentary</rule>

    <order direction="ascending">title</order>

</smartplaylist>

[jjd-uk]

Yes that's the other way of doing it, however you will have to manually configure a widget for every single Genre used in your library which is a laborious task if your library contains a lot of Genres.

[mYnDstrEAm]

Also this is about a preconfigured view that's available by-default with the default-installation of Kodi. It's not about a way for a very small 0.5% group of experienced powerusers that are tech-savvy plus have the time, skills and interest to first know that this is what they want to have, then to successfully look up how it could be done and then manually individually implement it (same goes for the proposed multi-genre-multi-item view). Imagine if people were expected to locate, edit and configure xml files on their devices just to be able to view documentaries on popular online streaming services.

The info is useful nevertheless, as it may make the (first version of the) feature easier to implement. However, making use of such a playlist in some new default view somehow (and I don't know how) wouldn't solve the problem of documentaries cluttering the Movies page. I'd like to have Movies to only show movies (and a Documentaries tab in the left panel that only shows documentaries albeit with a multi-genre-multi-item view this could be added long afterward).

Edit:

Another way this could be solved that I didn't think of and wasn't mentioned so far is changing the left panel on the Movies page.

In the left panel of the Movies page one could add something like "bookmarked filters". These could be presets of the Filter above (in that left panel) or smart playlists.

They could also be applied (toggled on or off) via keyboard shortcuts. They could not only be preconfigured filters but also for example order. There could be many ways one could add such a filter to the sidepanel which wouldn't require lots of changes to Kodi and the skin. For example, one could configure it simply by changing the filters and so on of the view and then click on a small "Save filtered view" button. Next to the filters there could be minus signs to remove the bookmarked filter from the panel.

Other than that and maybe until better solutions, approximations to what has been proposed could get implemented: for example an easily findable toggle option in the settings to show "Documentaries" as a main menu item with the suboption (enabled if that is switched on) to filter it from the Movies page.