Additionally, I've observed that if I write *wiki* to place that smiley, the plugin requires the slug to be written in curly braces before and using colons before and after the smiley -> example: {freystatt}:*wiki*:

Is it possible to avoid this?

This is not possible for the following reason.

As far as wpForo Emotions addon contains several packages and it allows to create more packages by the forum owners, the slug has the following look: {folder_name}:smile_name:

{folder_name}:: -will be generated by the plugin 

smile_name - unique name added by the forum owner.

So you can have the "smile" emoticon in each package. In this case, to allow all smiles to be displayed correctly we've generated such a slug.

Regarding the issue.

Please see the screenshot below:

3539,3540

The correct name must be a wiki, not a *wiki*.

The name MUST NOT contain any symbols like *,/,- etc. The name must contain only Latin letters, not numbers and other symbols.

Additionally, I've observed that if I write *wiki* to place that smiley, the plugin requires the slug to be written in curly braces before and using colons before and after the smiley -> example: {freystatt}:*wiki*:

Is it possible to avoid this?

On a second, it seems that the smiley button that opens the smiley selection menu below on PC does not trigger that behavior on mobile (Huawei P20 Pro).

3536

It seems that the plugin has some problems with >, :, ( or ),

because all other smileys like *wiki* work fine.

3537

For the first "Smile" with ":)" 
3533

A different image for the second "Zwinkernd" with ";)"
3534

A different image for the third "Traurig" with ":("

3535

And so on.

Please let us know how have you tried to write the names of the smiles? Are you set it something like the following one (I mean jus a symbol)? 

:   )) 

Please try to write a unique name something like "Smile", "Sad", etc.  

It works now - but I run into another bug.

After uploading the 4th custom smiley, the previous smiley-images were overwritten as shown below.

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A refresh (F5 / CTRL + F5) did not work.

This behavior is kept - even when adding new smileys.

3528

The issue is fixed by our developers. Please check it. 

When have you sent the admin login details? We haven't found it. Could you please PM me the login details? 

The folder access rights are set to 755.

Unfortunately there is neither logging, a debug mode or console output - just an error pop-up in the upper right.

I've sent you an email too. 

Regards, 

Martin