[snap] All open windows are grouped under one single icon in the dock

I can reliably observe the issue on bionic too.

This is caused by libreoffice's application architecture: there's one single process for all open windows, so all windows get matched to the desktop file corresponding to the first app launched.

I.e. if I first launch the start center (libreoffice), all the windows will get the generic document icon. If I first launch writer (libreoffice.writer), all the windows will get the text document icon.

Not really sure what can be done about this.

i dont know if it helps, but if i recall correctly in unity was a similar bug and it was resolved.
Now in unity you see the secuence for any app of libreoffice
1.- Click in application
2.- In the dock, opens the white icon
3.- When app start, the dock show the correct icon.

I can confirm this for LO 6.1 on Ubuntu 18.04 Bionic Beaver.

snap version
snap 2.36.3
snapd 2.36.3
series 16
ubuntu 18.04
kernel 4.16.18-041618-generic

snap info libreoffice
name: libreoffice
summary: LibreOffice is a powerful office suite including word processing and creation of spreadsheets,
  slideshows and databases
publisher: Canonical✓
contact: https://bugs.launchpad.net/ubuntu/+source/libreoffice/+bugs?field.tag=snap
license: unset
description: |
  LibreOffice is a powerful office suite – its clean interface and
  feature-rich tools help you unleash your creativity and enhance your
  productivity. LibreOffice includes several applications that make it the
  most powerful Free and Open Source office suite on the market: Writer (word
  processing), Calc (spreadsheets), Impress (presentations), Draw (vector
  graphics and flowcharts), Base (databases), and Math (formula editing).
commands:
  - libreoffice.base
  - libreoffice.calc
  - libreoffice.draw
  - libreoffice.filebug
  - libreoffice.impress
  - libreoffice
  - libreoffice.math
  - libreoffice.writer
snap-id: CpUkI0qPIIBVRsjy49adNq4D6Ra72y4v
tracking: stable
refresh-date: 2 days ago, at 16:29 GMT
channels:
  stable: 6.1.4.2 (100) 499MB -
  candidate: 6.1.4.2 (100) 499MB -
  beta: ↑
  edge: ↑
installed: 6.1.4.2 (100) 499MB -

I just want to add, in kubuntu plasma the problem does not exist. Each libreoffice application (writer, impress, calc, draw) is associated with its icon in the panel.

lsb_release -d
Description: Ubuntu 18.10

snap --version
snap 2.37.4+18.10.1
snapd 2.37.4+18.10.1
series 16
ubuntu 18.10
kernel 4.18.0-16-generic

name: libreoffice
summary: LibreOffice is a powerful office suite including word processing and creation of spreadsheets,
  slideshows and databases
publisher: Canonical✓
contact: https://bugs.launchpad.net/ubuntu/+source/libreoffice/+bugs?field.tag=snap
license: unset
description: |
  LibreOffice is a powerful office suite – its clean interface and feature-rich tools help you
  unleash your creativity and enhance your productivity. LibreOffice includes several applications
  that make it the most powerful Free and Open Source office suite on the market: Writer (word
  processing), Calc (spreadsheets), Impress (presentations), Draw (vector graphics and flowcharts),
  Base (databases), and Math (formula editing).
commands:
  - libreoffice.base
  - libreoffice.calc
  - libreoffice.draw
  - libreoffice.filebug
  - libreoffice.impress
  - libreoffice
  - libreoffice.math
  - libreoffice.writer
snap-id: CpUkI0qPIIBVRsjy49adNq4D6Ra72y4v
tracking: stable
refresh-date: 12 days ago, at 16:13 -03
channels:
  stable: 6.2.1.2 2019-03-10 (106) 507MB -
  candidate: 6.2.2.2 2019-03-25 (110) 506MB -
  beta: 6.2.0.3 2019-01-31 (103) 505MB -
  edge: ↑
installed: 6.2.1.2 (106) 507MB -

I confirm this also in Ubuntu 20.04, with LO 6.4.3.2, installed by Ubuntu Software 3.36.1

Snap version 7.2.1.2, problem still here. U20.04