slideshow.staytime raise maximum to 3600 in settings.xml

Hello, I have the following problem:

Requirement:

Want to set the staytime of displaying an image of slideshow longer than 100 seconds (to 3600 seconds).

System:

LibreELEC (official): 9.1.501 (RPi4.arm) (also tried with 8.2 on RPI3)

What I've tried to do:

Changing <maximum> etc. in

/usr/share/kodi/system/setting/settings.xml

from

<setting id="slideshow.staytime" type="integer" label="12378" help="36312">
<level>0</level>
<default>5</default>
<constraints>
<minimum>1</minimum>
<step>1</step>
<maximum>100</maximum>
</constraints>
<control type="spinner" format="string">
<formatlabel>14045</formatlabel>
</control>
</setting>

to

<setting id="slideshow.staytime" type="integer" label="12378" help="36312">
<level>0</level>
<default>5</default>
<constraints>
<minimum>10</minimum>
<step>10</step>
<maximum>3600</maximum>
</constraints>
<control type="spinner" format="string">
<formatlabel>14045</formatlabel>
</control>
</setting>

which leads to error "Read-only file system".

Therefore I've tried this, too:

mount -o remount,rw /flash

and, because /usr folder is on /dev/loop0

mount -o remount,rw /dev/loop0

also restarted system after changes.

But /dev/loop0 state is still on ro.

Question:

How can I overwrite files in /usr ? Or is it possible to extend settings.xml on other location to overwrite some values? In advancedsettings.xml I didn't fount any parameters could have to do something with those.