I think it's possible with a template too,
Template:LockHide could be modified so that in can include many usernames:
{{LockHide|LillianaTillery|GailHarvill613|RobtPiddington}}

And then we get this URL that let you lock all accounts given in template:
https://meta.wikimedia.org/wiki/Special:MultiLock?wpTarget=LillianaTillery%0AGailHarvill613%0ARobtPiddington

We can also create a new template for multiple users.

That makes a lot more sense :-)

Perhaps {{MultiLock|...}} ?

I was hoping

[{{fullurl:Special:MultiLock|wpTarget={{#if:{{{1}}}|{{{1}}}}}{{#if:{{{2}}}|%0A{{{2}}}}}{{#if:{{{3}}}|%0A{{{3}}}}}{{#if:{{{4}}}|%0A{{{4}}}}}{{#if:{{{5}}}|%0A{{{5}}}}}}}]

would do the trick, but it prints:

username1
username2
username3
{{{4}}}
{{{5}}}

I should be able to create a template for this, but I won't be able to test it.

In T199769#4485272, @Stryn wrote:

I was hoping

[{{fullurl:Special:MultiLock|wpTarget={{#if:{{{1}}}|{{{1}}}}}{{#if:{{{2}}}|%0A{{{2}}}}}{{#if:{{{3}}}|%0A{{{3}}}}}{{#if:{{{4}}}|%0A{{{4}}}}}{{#if:{{{5}}}|%0A{{{5}}}}}}}]

would do the trick, but it prints:

username1
username2
username3
{{{4}}}
{{{5}}}

Is the only thing wrong with this the fact that the last two lines should not be there?

In T199769#4487308, @JJMC89 wrote:

Is the only thing wrong with this the fact that the last two lines should not be there?

Yep!

I wrote a script that may help, at https://meta.wikimedia.org/wiki/User:Enterprisey/multi-lock-helper.js. It adds a link in the section header with a link to Special:MultiLock.

Give @Aperson's script a try. It looks like a better solution than a template.

If you still want a template, let me know.

In T199769#4485272, @Stryn wrote:

I was hoping

[{{fullurl:Special:MultiLock|wpTarget={{#if:{{{1}}}|{{{1}}}}}{{#if:{{{2}}}|%0A{{{2}}}}}{{#if:{{{3}}}|%0A{{{3}}}}}{{#if:{{{4}}}|%0A{{{4}}}}}{{#if:{{{5}}}|%0A{{{5}}}}}}}]

would do the trick

This should work.

[{{fullurl:Special:MultiLock|wpTarget={{urlencode:{{{1|Example user}}}}}{{#if:{{{2|}}}|%0A{{urlencode:{{{2}}}}}}}{{#if:{{{3|}}}|%0A{{urlencode:{{{3}}}}}}}{{#if:{{{4|}}}|%0A{{urlencode:{{{4}}}}}}}{{#if:{{{5|}}}|%0A{{urlencode:{{{5}}}}}}}}} Lock all]

@APerson
your script is good, but it doesn't always give a "lock all" link in header ( for example here: https://meta.wikimedia.org/w/index.php?title=Steward_requests/Global&oldid=18284165#Global_lock_for_socks_of_Avoided_(or_an_impostor) because there is text before the account list ) and always requires a new header to work.

@JJMC89
Yes it works as I wanted :) Even better would be if it could show all account names on https://meta.wikimedia.org/wiki/Steward_requests/Global and add links "(talk • contribs • block • x-wiki • CA • lwcheckuser)" after every username as https://meta.wikimedia.org/wiki/Template:LockHide does.

I've created [[ https://meta.wikimedia.org/wiki/Template:MultiLock | {{MultiLock}} ]]. Let me know if it does what you want.