From anywhere
⌃⌥Space opens Start work in a floating panel over whatever app is in front. It takes the keyboard without bringing
Heed forward; ⎋ ⎋ or a click anywhere else closes it, and ⌘↩ starts the session.

Change the shortcut, or turn it off with "":
[keys]
global_start_work = "<C-M-Space>"
It needs no Accessibility permission. If another app owns the combination, the status bar says so.
The panel's window title is always Heed Start Work (app net.nullean.heed), so a tiling window manager can leave it
floating:
# OmniWM: ~/.config/omniwm/settings.toml (id is any UUID)
[[appRules]]
bundleId = "net.nullean.heed"
id = "75CF2DF1-FF34-4187-9CC9-01DD190EFC51"
layout = "float"
titleRegex = "^Heed Start Work$"
# yabai
yabai -m rule --add app="^Heed$" title="^Heed Start Work$" manage=off
Without a rule it still works: if a window manager takes focus the moment the panel opens, the panel takes it back.