app.py

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy.ext.associationproxy import association_proxy
from sqlalchemy.orm import relationship, backref

import flask_admin as admin
from flask_admin.contrib import sqla

# Create application
app = Flask(__name__)
app.config['SECRET_KEY'] = '123456790'
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite://'
app.config['SQLALCHEMY_ECHO'] = True
db = SQLAlchemy(app)

@app.route('/')
def index():
    return '<a href="/admin/">Click me to get to Admin!</a>'


entry_tags_table = db.Table(
    "entry_tags",
    db.Model.metadata,
    db.Column("entry_id", db.Integer, db.ForeignKey("entry.id")),
    db.Column("tag_id", db.Integer, db.ForeignKey("tag.id")),
)

class Entry(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String)
    tags = db.relationship("Tag", secondary=entry_tags_table, back_populates='entries')

class Tag(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.Unicode, nullable=False)
    entries = db.relationship("Entry", secondary=entry_tags_table, back_populates='tags')


class EntryAdmin(sqla.ModelView):
    column_searchable_list = [
        "title",
        "tags.name",
    ]

class TagAdmin(sqla.ModelView):
    pass


admin = admin.Admin(app, name='Test', template_mode='bootstrap4')
admin.add_view(EntryAdmin(Entry, db.session))
admin.add_view(TagAdmin(Tag, db.session))

if __name__ == '__main__':
    import sqlalchemy
    print(sqlalchemy.__version__)

    db.create_all()
    app.run(debug=True)