Adding translations to existing group misplaces keys

[danon]

You want to add "group.subgroup.key1000". Before:

'group' => [
    'key1' => 'value1',
    'key2' => 'value2'
]

After

'group' => [

    'subgroup' => [
        'key1000' => 'value100'
    ],              'key1' => 'value1',
    'key2' => 'value2'
]

Should be

'group' => [
    'subgroup' => [
        'key1000' => 'value100'
    ],              
    'key1' => 'value1',
    'key2' => 'value2'
]