How can I limit the length of the text, e.g., 50, and put three dots in the display?
{% if myentity.text|length > 50 %}
{% block td_text %} {{ myentity.text}
An even more elegant solution is to limit the text by the number of words (and not by number of characters). This prevents ugly tear throughs (e.g. 'Stackov...').
Here's an example where I shorten only text blocks longer than 10 words:
{% set text = myentity.text |split(' ') %}
{% if text|length > 10 %}
{% for t in text|slice(0, 10) %}
{{ t }}
{% endfor %}
...
{% else %}
{{ text|join(' ') }}
{% endif %}