If you created some migration config and then you renamed it later, there is a good chance it is still present in config and it can also break your migration UI for that migration group. To clear that out, check your config with drush cedit find id of config and run this in devel/php or drush php

Maybe you came to that annoying message when you want to save something in PHP Storm but it refuses to and gives you options "cancel" or "revert changes", usually happens around some config files, like settings.php. Why is this so? Probably because you didn't put write permissions to folder where phpstorm is trying to write its temp files.

When you set or override some variables in settings.php with $settings var and want to get it in your code, call it like this.

use Drupal\Core\Site\Settings;

$mySetting = Settings::get('some_setting', NULL);

I see many people use https://www.drupal.org/project/eck  module when they want to create new entites in drupal 8. But there is a problem with that. By default ECK module in UI doesn't create base fields, you can create bundles and then add fields to them.

Some times you dont want to add something to .gitignore, while it would be nice that there is some .gitignore-local version by default, there is not, so you need to find a different way to do this, the way to do is this.  Go to .git/info/exclude file and edit it like regular .gitignore file, add files/folders you want to ignore.

To have xdebug working, you need to have this in your docker config for PHP.

      PHP_XDEBUG: 1
      PHP_XDEBUG_DEFAULT_ENABLE: 1
      PHP_XDEBUG_REMOTE_CONNECT_BACK: 0
      PHP_XDEBUG_REMOTE_HOST: 10.254.254.254 # macOS, Docker < 18.03

Also it is often noted that this should also be run

After few examples pointed before, how to make links and urls,
https://www.drupaldump.com/making-url-anchorfragment-and-making-url-que…
https://www.drupaldump.com/some-ways-make-links-drupal-8

$options = ['fragment' => 'feedback'];
$url = Url::fromRoute('entity.node.canonical', ['node' => 22], $options);

$options = ['query' => ['animal' => 'dog', 'color' => 'black']];
$url = Url::fromRoute('entity.node.canonical', ['node' => 42], $options);

So first would give you  this result 

// Link to an internal path defined by a route.
$link = Link::createFromRoute('This is some link', 'entity.node.canonical', ['node' => 22])

// Link to an external URI.
$link = Link::fromTextAndUrl('This is a link', Url::fromUri('https://example.com'));

// Get output as a render array.
$link->toRenderable();

// Get output as a string.
$link->toString();

// From a route.
$url = Url::fromRoute('contact.site_page');
// From a URI.
$url = Url::fromUri('https://example.com');
// From route with additional parameters.
$url = Url::fromRoute('entity.node.canonical', ['node' => 22]);